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In your quest for the highest frame rates, the prettiest textures, and the

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most karma in the PC master race

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subreddit, you decided to go with a multi-GPU setup for your new gaming rig.

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But when you fire up your games, you notice that the sick gains you're

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getting aren't really what you expected, especially after

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dropping so much money on your system.

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So, what's the deal with that? Well, this problem has plagued PC gamers for

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over a decade. Why don't you usually get

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double the performance from a dual card configuration or triple if you have

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three video cards? I mean, since graphics rendering benefits from having

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more computing units in parallel, which you can learn more about in this video,

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by the way, wouldn't it make sense then for multicard setups like SLI and

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Crossfire to scale pretty easily?

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Unfortunately, it's not quite that simple. For starters, using two separate

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graphics cards means they have to talk to each other somehow. You see, most

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modern multiGPU setups use something called alternate frame rendering, where

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each card renders every other frame

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separately. Sounds efficient, but for

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them to be pushed to your monitor in the right order, the cards have to sync up

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properly, creating a surprising amount of overhead for both the GPUs and the

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electrical communication paths or buses that link them. This overhead not only

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gets worse as you add more cards to your rig, but can even result in a very

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unpleasant phenomenon called micro stuttering, which often shows up even if

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you're getting lots of frames per second. You see, for smooth gameplay,

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you need not only high FPS, but good and

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consistent frame times, which is the

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amount of time that a given frame will remain on your screen. Poor

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synchronization between the cards can leave certain frames on your monitor for

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way longer than they should be, even if the total number of frames each second

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is very high. This can render certain games

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unplayable, even though your setup is more than powerful enough to run it on

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paper. And as if that wasn't enough, an

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even bigger problem is that it's very difficult for your GPUs to know what

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frame to render next since it depends heavily on what the player chooses to

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do. The real time nature of game rendering makes it tough to parallelize

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in certain games among multiple GPUs,

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even with alternate frame rendering, as there isn't always a second frame or

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even part of a predicted one for your second card to work on. Of course, it

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isn't all about the inherent limitations of your hardware. On the software side,

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some game developers have been able to code their games in a manner that makes

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it easier for multiple GPUs to split the workload, while others simply don't

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bother. With the difficulty in coding for a very small subset of customers,

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many devs don't see the point in sinking

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tons of time into making sure that their games will play nice with multicard

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systems. Some games even manage to have worse performance in these situations.

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And finally, you definitely shouldn't run out and buy multiple GPUs if you're

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rocking a multiple monitor setup and you want extra video memory or VRAM to store

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all of your textures. With SLI and

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Crossfire, you are limited only to however much VRAM is on one card because

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both GPUs need to be able to access the same information in memory in order to

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work properly in tandem, whatever it might say on the packaging. So, does

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this mean then that SLI and Crossfire are useless gimmicks and a complete

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waste of money? Well, no. Multicard

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setups will give you the best possible performance in certain use cases and can

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even make some games playable at very high settings and resolutions where they

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wouldn't otherwise be, even with the best single card on the market. Not to

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mention that multiGPU rendering may improve with new APIs like Vulcan and

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DirectX12, which by the way you can learn more about here. Just do your

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research before you buy as to what games

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see the greatest benefit. And remember to keep your expectations realistic.

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After all, you wouldn't expect to be able to drive twice as fast just because

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you bought two cars, would you? Unless

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you're trying to do like a fan remake of Tokyo

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that linked in the video description. Thanks for watching, guys. Like if you

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